Get the average number from the middle of the list if the list is even or the middle number when the list is odd

getNumber.js

const isEven = (num) => (num % 2 === 0)

const getNumber = (array = []) => {
    const size = array.length
    if(isEven(size)){
        const index = size/2
        return (array[index]+array[index-1])/2
    }
    const index = (size-1)/2
    return array[index]
}

console.log(getNumber([1,4,5])); // 4
console.log(getNumber([1,4,5,6])); // 4.5
console.log(getNumber([1,4,5,6])); // 4.5
console.log(getNumber([1,4,5,6,8])); // 5
console.log(getNumber([1,4,5,5,8,3])); // 5